Aircraft maintenance, including reliable troubleshooting, is of paramount importance to ensure the continued safe and efficient operation of aircraft. Aircraft maintenance can occur in several different manners. For example, scheduled maintenance generally includes a number of specific tasks, inspections and repairs that are performed at predetermined intervals. These events are scheduled in advance and rarely result in aircraft schedule interruption. In contrast, unscheduled maintenance is performed as required to maintain the aircraft's allowable minimum airworthiness during intervals between scheduled maintenance. Unscheduled maintenance is usually performed while the aircraft is on the ground between flights. However, unscheduled maintenance may be performed during a scheduled maintenance check if a mechanic identifies a problem that was not anticipated. Minimum ground time between flights is desirable to maximize aircraft utilization and to meet the established flight schedules. Therefore, the time allocated to unscheduled maintenance is often limited to the relatively short time that the aircraft is required to be at the gate in order to permit passengers to unload and load, to refuel and to otherwise service the aircraft.
Although modern datalink communications facilitate preflight troubleshooting by allowing pilots or maintenance operators to note a problem (e.g., component failure) during the last flight leg or while the aircraft is on the ground, it is oftentimes difficult to troubleshoot the aircraft and complete unscheduled maintenance before the departure time of the next scheduled flight for the aircraft, thereby leading to flight delays and/or cancellations. These flight delays and/or cancellations are extremely costly to an airline, both in terms of actual dollars and in terms of passenger perception. In this regard, an airline typically begins accruing costs related to a flight delay following the first five minutes of a delay, with substantial costs accruing if the flight must be cancelled. Moreover, and as all air passengers are aware, airline dispatch reliability is a sensitive parameter that airlines often use to distinguish themselves from their competitors.
Notwithstanding the critical importance of properly performing unscheduled maintenance in both an accurate and timely manner, mechanics who perform the troubleshooting and unscheduled maintenance on the flight line face a daunting challenge. Aircraft are extremely large and complex systems comprised of many interconnected subsystems. Each subsystem is typically comprised of many LRUs (line replaceable units) that are designed to be individually replaced. An LRU may be mechanical, such as a valve or a pump; electrical, such as a switch or relay; or electronic, such as an autopilot or a flight management computer. Many LRUs are, in turn, interconnected. As such, the symptoms described by flight deck effects or other observations may indicate that more than one LRU can explain the presence of the observed symptoms. At that point, there is ambiguity about which LRU(s) have actually failed. Additional information will be needed to disambiguate between the possibilities. The above notwithstanding, ambiguous fault indications discovered during the troubleshooting process must nevertheless be resolved before the aircraft can be dispatched. Although such is not always the case, the ambiguous faults are ideally resolved within the cost functions, cost limits, airline schedule time constraints, airworthiness guidelines (e.g., “minimum equipment list” (MEL)), maintenance crew expertise at current location and at future destinations, part replacement costs, labor availability, repair equipment availability, part availability, size of next destination airport and its type of runway surface, etc.
Aircraft personnel must decide what tests and remedial actions to make when operational problems arise that threaten to delay an aircraft flight. These decisions must consider alternatives available and potential outcomes. Moreover, some maintenance actions cannot be deferred (e.g., actions in the airline's MEL guidelines), while other maintenance actions can be deferred (e.g., repair of components on the MEL list such as a coffee maker, a flight attendant call button, etc.). In short, aircraft preflight dispatch decision-making is a diagnostic process constrained by available alternatives and outcome values.
In an effort at least in part to assist aircraft personnel with troubleshooting and unscheduled maintenance, improved diagnostic systems and methods have been provided as is thoroughly described in the copending application titled “DIAGNOSTIC SYSTEM AND METHOD” of Kipersztok, et al., U.S. Pat. No. 6,574,537, filed Feb. 5, 2001, issued Jun. 3, 2003, which is commonly assigned with the present application. The entire contents of U.S. Pat. No. 6,574,537 is incorporated herein by reference in its entirety. The diagnostic systems and methods of U.S. Pat. No. 6,574,537 allow for reliable, time-efficient identification of failed components and provide information to enable aircraft personnel to make informed and efficient decisions regarding repair of suspect components or deferral of maintenance actions.
Although the diagnostic systems and methods of U.S. Pat. No. 6,574,537 have been successful for their intended purposes, it would also be highly desirable to provide a diagnostic system and method that determines the optimal maintenance action to take instead of aircraft personnel whose decisions might result in cost functions, cost limits, and time deadlines being exceeded during the aircraft preflight dispatch diagnostic process.